President Barack Obama defended controversial new security measures at U.S. airports in an interview released on Friday, saying the methods were necessary to prevent a potential terrorist attack.

Some Americans have objected in recent weeks to the use of revealing full-body scanners and extra-thorough patdowns at airport security checkpoints.

“This is going to be something that evolves. We are going to have to work on it,” Obama told ABC’s Barbara Walters, according to a transcript provided by the network.

“I understand people’s frustrations with it but I also know that if there was an explosion in the air that killed a couple of hundred people … and it turned out that we could have prevented it possibly … that would be something that would be pretty upsetting to most of us — including me.”